our 5yr old male that died had a exp about 2 yrs age like yours.
one of our rescue dogs(very lg boxer) jumped a series of fences and went after the deer. Timmy the male jumped the fence into the horse pasture and didnt quite make it, he landed on his head and broke his neck, he dislocated the vertibre. anyway it took us about 2 months to rehab him. various technics, alot of muscle relaxer and anti inflams. he could not stand for about 1 week and could not walk without falling down the rest of the 2 months until the spinal cord swelling went down, he did fully recover. my point is, in my exp deer are tough (unlike goats who will just lay down and die) if they look like they want to live, keep it up. it may take a while they will find a way to overcome it. good luck